Background: Gastric cancer is one of the major causes of cancer-related mortality worldwide. Most of patients presenting with inoperable gastric cancers rely on systemic chemotherapy for prolongation of survival. Doxorubicin (DOX) is one of the important agents against gastric cancer. Acquired DOX-resistance severely impedes the chemotherapeutic effect, invariably leading to poor prognosis. Resveratrol (RES) as a kind of phytoalexin has demonstrated anti-tumor functions in breast cancer and myeloid leukemia, but its function and mechanism are still unknown in gastric cancer treatment.
Methods: CCK8 assay was used to detect the cytotoxicity of DOX and RES to gastric cancer cells. DOX-resistant subclone cell line (SGC7901/DOX) was derived from SGC7901 cells exposed to stepwise increasing concentrations of DOX treatment. We measured the migratory capabilities of SGC7901/DOX cells by Cell scratch test and Transwell assay. SGC7901/DOX cells were treated with DOX, RES, neither or both. Then we analyzed cell survival by CCK8 assay, colony formation by Colony-forming assay, cell apoptosis by Annexin-V-FITC and PI dual staining assay and cell migration by Cell scratch test and Transwell assay. Western blotting was conducted to detect the protein expressions of PTEN/Akt signaling pathway and EMT-related markers. Immunofluorescence was performed to confirm the EMT-related markers expressions. The xenograft model was used to assess the effect of DOX and RES in vivo. The key molecules associated with proliferation, apoptosis and EMT were evaluated by immunohistochemistry in tumor specimens.
Results: SGC7901/DOX cells acquired drug resistance and enhancive migratory capability. RES enabled SGC7901/DOX cells to regain DOX sensitivity, mitigated the aggressive biological features, promoted cell apoptosis in vitro and inhibited tumor growth in vivo. Mechanistic studies revealed that SGC7901/DOX cells underwent epithelial-mesenchymal transition (EMT) which was induced by Akt activation, and through activating PTEN, RES inhibited the Akt pathway, and then achieved the reversion of EMT.
Conclusion: RES serves as a novel solution to reverse the DOX-resistance of gastric cancer via preventing EMT by modulating PTEN/Akt signaling pathway. DOX-RES combined treatment provides a promising future for gastric cancer patients to postpone drug resistance and prolong survival.
Keywords: Doxorubicin; Drug resistance; EMT; PTEN/Akt; Resveratrol.